1. Field of the Invention
The present invention relates to a control method and a control system for stably performing a parallel operation of different types of power generation apparatuses having respective different drooping characteristics.
2. Description of Related Art
In some of the marine vessels of an electric propulsion system, two power generation apparatuses driven by respective prime movers are generally employed so that during a normal (low speed) marine navigation, only one of the prime movers is activated for economical navigation, and during an abrupt acceleration or a high speed marine navigation, both of the prime movers are operated in parallel with each other. In this respect, see, for example, the patent document 1 listed below. In this way, the two performances, that is, the marine cruising radius and the acceleration/speed characteristic, may be simultaneously pursued. For further efficient marine navigation, it may be contemplated to use two different types of prime movers, for example, a diesel engine and a gas turbine engine.
In various electric power source facilities, a power generation apparatus, which is regularly put into operation, and a power generation apparatus, which is put into operation in the event of an emergency or an acute situation are differentiated from each other depending on the type of the engine prime mover, and the parallel operation of the power generation apparatuses having different types and/or characteristics are not generally practiced. In addition, in the event of occurrence of any trouble in a portion of the regularly operated device or where a peak-cut operation with the use of a standby apparatus is desired because of a considerable change in load, it is a general practice to operate power generation apparatuses, including the standby apparatuses, that have been so adjusted in advance to be the same type and to have the same drooping characteristics.
In the case of an arbitrary shutdown of various power generation apparatuses forming an electric power source system, or in the case of electric power source facilities of a natural energy recovering type that undergoes significant changes depending on times of a day and/or ambient environments, changes appear in the rotation number (frequency) drooping characteristic on the side of the electric power source system and also in the impedance of the system power source side at all times. For such electric power source facilities, a control method and a control system, which are capable of optimally switching by changing arbitrarily the drooping characteristic of the power generation apparatuses, that are to be parallel operated with the system side, in dependence on a change of the system power source (electric power generation facilities in operation forming the system) of the power generation apparatus forming a part of such electric power source facilities to suit characteristics between the power generation apparatuses forming the electric power source facilities, are considered as required.